Plate heat exchanger with flow directing baffles

ABSTRACT

A plate heat exchanger includes a stack of plate pairs arranged within a housing. Comb-like baffles extend into flow gaps between the plate pairs to direct a fluid flow in a sinusoidal pattern within the flow gaps. The flow gaps are divided into two sub-sets of flow gaps, preferably alternatingly arranged along the height of the stack. Legs of some baffles extend into a first sub-set but not into the second sub-set, while legs of some baffles extend into the second sub-set but not into the first sub-set. The baffles are arranged so that the sinusoidal pattern in the second sub-set is phase-shifted form the sinusoidal pattern in the first sub-set.

BACKGROUND

The present invention relates to heat exchangers, and particularly to plate heat exchangers.

Plate heat exchangers are used to transfer heat between two fluids, typically two liquids. In one common construction of such a heat exchanger, the plates are arranged in pairs and are assembled into a stack. The plates of the stack are commonly joined together by brazing to form a monolithic structure with internal flow structures through which one of the fluids is circulated while the other fluid passes over outer surfaces of the plates. The two fluids are thereby placed into heat transfer with one another, while remaining physically separated from each other.

Plate heat exchangers of the aforementioned kind can be placed within a housing or housing in order to contain, and channel, the externally flowing fluid.

While flow turbulation features such as fins or inserts can be readily inserted into each of the plate pairs in order to route the internally flowing fluid, and to provide enhanced convective heat transfer for that fluid, the outer surfaces of the plate pairs are often not so enhanced. This can result in the overall heat exchanger effectiveness being limited by the rate of convective heat transfer between the outer surfaces of the plate pairs and the externally flowing fluid.

SUMMARY

A plate heat exchanger exhibiting high thermal effectiveness is provided by way of a stack of plates arranged within a housing, the housing defining a volume for a fluid to flow through. The fluid can be a liquid, for example a coolant such as water or glycol or a water/glycol mixture. The fluid can alternatively be another liquid, such as an oil. Still alternatively, the fluid can be a gas.

The fluid passing through the volume is in heat transfer with another fluid that flows through internal structures of the plates. This heat transfer can result in the transfer of thermal energy from the other fluid to the fluid flowing through the volume, so that the fluid flowing through the volume serves to cool the other fluid. Alternatively, the heat transfer can result in the transfer of thermal energy from the fluid flowing through the volume to the other fluid, so that the fluid flowing through the volume serves to heat the other fluid.

The fluid flowing through the plates can be a liquid, such as an oil. Alternatively, the fluid flowing through the plates can be a gas, or a two-phase fluid that is at times a liquid and at other times a gas. In such cases, the plate heat exchanger can be used to condense the other fluid from a gas phase to a liquid phase as the other fluid flows through the plates, or to vaporize the other fluid from a liquid phase to a gas phase as the other fluid flows through the plates. In one particular such application, the plate heat exchanger can be employed as a vaporizer for liquified natural gas (LNG) or liquified petroleum gas (LPG) in an engine system that uses LNG or LPG as a fuel.

The plates within the stack can be arranged in pairs, so that each pair of plates forms a plate assembly though which the other fluid can flow. A turbulating insert can be arranged within each such plate pair to reinforce the plate pair against internal pressurization or to increase the rate of heat transfer within the plate pair or both. Faces of adjacent ones of the plate pairs can be spaced apart so that flow gaps are arranged between them. This allows for the fluid passing through the volume to pass over those faces in order to efficiently exchange thermal energy with the other fluid that is simultaneously passing through the plate pair. An additional flow gap can be provided between outermost ones of the plate pairs (e.g. the terminal plate pair at each end of the stack in the stacking direction) and walls of the housing.

The geometry of the plate pairs can be such that the plate pair has a greater dimension in one direction (the longitudinal direction) than in the other direction (the transverse direction). This allows for more effective overall heat transfer, since both fluids can be directed to flow in the longitudinal direction.

The plate heat exchanger can also be provided with comb-like baffles that extend into the flow gaps to direct the flow of the fluid as it passes through the flow gaps. These comb-like baffles can be arranged to cause the fluid to be repeatedly directed to flow in the transverse direction as it moves in an overall longitudinal direction through the flow gaps. This has the effect of increasing the overall length of the flow path, and results in a greater rate of convective heat transfer due to higher Reynolds numbers in the fluid flow. The alternating back-and-forth movement of the fluid in the transverse direction as the fluid moves in an overall longitudinal direction creates a sinusoidal flow path for the fluid within each flow gap.

The flow gaps can consist of a first and a second subset of flow gaps. The flow gaps of the first subset can be alternatingly arranged with the flow gaps of the second subset. In some embodiments, however, the flow gaps of the first and the second subset can be arranged in other patterns.

The baffles can be used to define a sinusoidal flow path in each of the flow gaps of the second subset that is phase-shifted from a sinusoidal flow path that the baffles define in each of the flow gaps of the first subset. By phase-shifted is meant that the sinusoidal flow pattern in each of the flow gaps of the second subset are offset in the longitudinal direction from the sinusoidal flow pattern in each of the flow gaps of the first subset by a generally fixed distance, which can be expressed as a percentage of the period of the sinusoidal flow pattern. This percentage can be expressed as an angular phase shift by considering the full period of the sinusoidal flow pattern to be equal to 360°.

The phase-shifting of the sinusoidal flow patterns in the first and second subsets of flow gaps can be used to minimize the undesirable heat transfer impact of convective dead zones that tend to occur immediately downstream of each baffle. As the baffles block the flow of the fluid in the longitudinal direction and cause it to flow in the transverse direction, the fluid will have a higher mean velocity at the upstream face of the flow baffle and a lower mean velocity at the downstream face, with corresponding higher Reynolds numbers and heat transfer coefficients at the upstream faces and corresponding lower Reynolds numbers and heat transfer coefficients at the downstream faces.

When the flow gaps of the first subset and the flow gaps of the second subset are alternatingly arranged, each plate pair will have one plate bounding a flow gap of the first subset and one plate bounding a flow gap of the second subset. By phase-shifting the sinusoidal flow patterns on either side of the plate pair, the regions of lower heat transfer on one plate of the pair can be made to align with regions of higher heat transfer on the other plate of the pair. This can result in better overall heat transfer effectiveness of the heat exchanger.

In some embodiments, the sinusoidal flow paths in flow gaps of the second subset are phase shifted from the sinusoidal flow paths in the flow gaps of the first subset by 180° In other embodiments, the sinusoidal flow paths in flow gaps of the second subset are phase shifted from the sinusoidal flow paths in the flow gaps of the first subset by no more than 90°. This can lead to a more uniform rate of overall heat transfer along the longitudinal direction. In some particular embodiments of this kind, the sinusoidal flow paths in flow gaps of the second subset are phase shifted from the sinusoidal flow paths in the flow gaps of the first subset by approximately 60°. In other embodiments, the sinusoidal flow paths are phase shifted by an amount between 60° and 90°, and in still other embodiments the sinusoidal flow paths are phase shifted less than 60°.

Outwardly directed dimples can be provided on the plates to provide the desired spacing between the plate pairs. These dimples can be arranged in a repeating pattern, with dimples of adjacent plates that face each other aligned so that the dimples abut one another, thereby creating the flow gaps. The plate pairs can be joined together by way of such abutting dimples, by braze joints for example, to create a monolithic stack structure.

The dimple pattern can be constructed so that the dimples are arranged in rows that extend in the transverse direction. This can allow the comb-like baffles to be arranged between the rows of dimples. In some embodiments the dimple pattern is a grid-like pattern, with the dimples arranged in columns that extend in the longitudinal direction as well as in rows that extend in the transverse direction. Such a dimple pattern can be a staggered pattern, wherein alternating rows have dimples in alternating columns. Alternatively, such a dimple pattern can be an unstaggered pattern. The dimple pattern can also provide an arrangement of dimples in rows that are oriented at a non-perpendicular angle to both the longitudinal and the transverse directions. Such an arrangement can allow for baffles that extend into the flow gaps between such rows at an angle to the transverse direction.

Each of the plate pairs can be provided with a first edge and a second edge that both extend in the longitudinal direction of the plate pair. The plate heat exchanger can include one or more first flow baffles arranged within the housing. In some embodiments the plate heat exchanger has only one such first flow baffle, while in other embodiments the plate heat exchanger has more than one such first flow baffle. Each of the one or more first flow baffles can be provided with legs that extend from the first edges of the plate pairs into some, but not all, of the flow gaps. The legs extend into a first subset of the flow gaps, but not into a second subset of the flow gaps. In this way, the legs of the first flow baffles serve to deflect the fluid flowing in the first subset of the flow gaps but do not affect the fluid flowing in the second subset of the flow gaps.

The legs of the first flow baffles can, in some embodiments, extend over more than half of the dimension of the plate pairs in the transverse direction. Such an extension of the legs can serve to adequately direct the fluid flowing in the first subset of the flow gaps in the transverse direction, away from the first edges. The legs can have terminal ends that are spaced away from the second edges of the plate pairs, i.e. located between the first edges and the second edges along the transverse direction. This can allow for the fluid flowing in the first subset of the flow gaps to flow between those terminal ends and a wall of the housing that is located adjacent to the second edges, so that the flow of fluid can continue along the longitudinal direction.

The plate heat exchanger can also include one or more second flow baffles arranged within the housing. In some embodiments the plate heat exchanger has only one such second flow baffle, while in other embodiments the plate heat exchanger has more than one such second flow baffle. Each of the one or more second flow baffles can be provided with legs that extend from the second edges of the plate pairs into some, but not all, of the flow gaps. The legs of the one or more second flow baffles can extend into the second subset of the flow gaps but not into the first subset, so that the legs of the second flow baffles deflect the fluid flowing in the second subset of the flow gaps but do not affect the fluid flowing in the first subset of the flow gaps.

The legs of the second flow baffles can, in some embodiments, extend over more than half of the dimension of the plate pairs in the transverse direction. Such an extension of the legs can serve to adequately direct the fluid flowing in the second subset of the flow gaps in the transverse direction, away from the second edges. The legs can have terminal ends that are spaced away from the first edges of the plate pairs, i.e. located between the first edges and the second edges along the transverse direction. This can allow for the fluid flowing in the second subset of the flow gaps to flow between those terminal ends and a wall of the housing that is located adjacent to the first edges, so that the flow of fluid can continue along the longitudinal direction.

The plate heat exchanger can also include one or more third flow baffles arranged within the housing. In some embodiments the plate heat exchanger has only one such third flow baffle, while in other embodiments the plate heat exchanger has more than one such third flow baffle. Each of the one or more third flow baffles can be provided with legs that extend from the second edges of the plate pairs into the first subset of the flow gaps but not into the second subset, so that the legs of the third flow baffles deflect the fluid flowing in the first subset of the flow gaps but do not affect the fluid flowing in the second subset of the flow gaps.

The legs of the third flow baffles can, in some embodiments, extend over more than half of the dimension of the plate pairs in the transverse direction. Such an extension of the legs can serve to adequately direct the fluid flowing in the first subset of the flow gaps in the transverse direction, away from the second edges. The legs can have terminal ends that are spaced away from the first edges of the plate pairs, i.e. located between the first edges and the second edges along the transverse direction. This can allow for the fluid flowing in the first subset of the flow gaps to flow between those terminal ends and a wall of the housing that is located adjacent to the second edges, so that the flow of fluid can continue along the longitudinal direction.

The plate heat exchanger can also include one or more fourth flow baffles arranged within the housing. In some embodiments the plate heat exchanger has only one such fourth flow baffle, while in other embodiments the plate heat exchanger has more than one such fourth flow baffle. Each of the one or more fourth flow baffles can be provided with legs that extend from the first edges of the plate pairs into the second subset of the flow gaps but not into the first subset, so that the legs of the third flow baffles deflect the fluid flowing in the second subset of the flow gaps but do not affect the fluid flowing in the first subset of the flow gaps.

The legs of the fourth flow baffles can, in some embodiments, extend over more than half of the dimension of the plate pairs in the transverse direction. Such an extension of the legs can serve to adequately direct the fluid flowing in the second subset of the flow gaps in the transverse direction, away from the first edges. The legs can have terminal ends that are spaced away from the second edges of the plate pairs, i.e. located between the first edges and the second edges along the transverse direction. This can allow for the fluid flowing in the second subset of the flow gaps to flow between those terminal ends and a wall of the housing that is located adjacent to the second edges, so that the flow of fluid can continue along the longitudinal direction.

In some embodiments, each of the one or more first flow baffles is aligned with one of the one or more second baffles in the longitudinal direction. In some embodiments, each of the one or more third flow baffles is aligned with one of the one or more fourth baffles in the longitudinal direction. In other embodiments, the first, second, third, and fourth flow baffles are all staggered along the longitudinal direction, and in some such embodiments they are arranged in a repeating pattern along the longitudinal direction.

In some embodiments where the flow baffles are arranged in a repeating pattern, the repeating pattern consists of one of the first flow baffles followed by one of the second flow baffles followed by one of the third flow baffles followed by one of the fourth flow baffles. Such a repeating pattern can include a uniform spacing between consecutive flow baffles, or it can include a non-uniform spacing. In some embodiments with a non-uniform spacing, a spacing in the longitudinal direction between the first and the second flow baffles of the repeating pattern is greater than a spacing in the longitudinal direction between the second and the third flow baffles in the repeating pattern. In some such embodiments, the spacing between the first and the second flow baffles is exactly twice the spacing between the second and the third flow baffles.

A repeating pattern with non-uniform spacing can still have some equal spacings between members of the pattern. For example, in some embodiments where the spacing in the longitudinal direction between the first and the second flow baffles of the repeating pattern is greater than the spacing in the longitudinal direction between the second and the third flow baffles in the repeating pattern, the spacing in the longitudinal direction between the third and the fourth flow baffles of the repeating pattern can be equal to the spacing between the first and the second flow baffles of the repeating pattern. Similarly, the spacing in the longitudinal direction between the fourth flow baffle of one instance of the repeating pattern and the first flow baffle of an immediately following instance of the repeating pattern can be equal to the spacing in the longitudinal direction between the second and the third flow baffles of the repeating pattern.

It can also be possible, in those embodiments where the flow baffles are arranged in a repeating pattern having a non-uniform spacing, for the flow baffles having legs that extend into the same subset of flow gaps to be uniformly spaced from one another. For example, the spacing between successive ones of the first and third flow baffles, or the spacing between successive ones of the second and fourth flow baffles, can be a constant spacing. In some embodiments a first constant spacing between successive ones of the first and third flow baffles can be equal to a second constant spacing between successive ones of the second and fourth flow baffles. In some such embodiments the first flow baffles are spaced apart from the successive second flow baffles by an amount less than those first and second constant spacings.

The legs of the flow baffles extending into the flow spaces can direct the fluid to flow through those spaces in a sinusoidal pattern. For example, in the flow spaces of the first subset, the fluid is alternatingly directed to flow in opposite transverse directions (i.e. from the first edge towards the second edge, and from the second edge towards the first edge) by alternatingly encountering the legs of the one or more first flow baffles and the legs of the one or more third flow baffles. Similarly, in the flow spaces of the second subset, the fluid is alternatingly directed to flow in opposite transverse directions by alternatingly encountering the legs of the one or more second flow baffles and the legs of the one or more fourth flow baffles.

When those flow baffles that have legs extending into the same subset of flow gaps are uniformly spaced from each other along the longitudinal direction with a constant spacing, then the resulting sinusoidal flow pattern will have a period that is equal to two times that constant spacing.

In those cases where the baffles whose legs extend into the first subset of flow gaps (e.g. the first flow baffles and the third flow baffles) are offset in the longitudinal direction from the baffles whose legs extend into the second subset of flow gaps (e.g. the second flow baffles and the fourth flow baffles), the resulting sinusoidal flow patterns in the first and second subsets will likewise be offset. When those sinusoidal flow patterns in the first and second subsets have an identical period, then the offset will result in the sinusoidal flow patterns being phase-shifted. The amount of phase shift can be expressed in degrees, based on the fraction of the period that the offset represents, a full period being equal to 360°. In some exemplary embodiments, the phase shift is equal to 60°, meaning that the offset is one sixth of a period. However, in other embodiments the phase shift can be less than or greater than 60°.

When the pairs of plates are spaced apart from one another by dimples that outwardly protrude from the plates, and those dimples are arranged in regularly spaced rows that extend in the transverse direction, then it can be advantageous to locate the flow baffles along the longitudinal direction such that the legs of each flow baffle extend in gaps between the rows of dimples. In such embodiments, the spacings between any of the flow baffles will be some integer multiple of the regular spacing between the rows of dimples.

Causing the fluid to flow in phase-shifted sinusoidal patterns in the first and second subsets of the flow gaps can result in enhanced heat transfer rates between the fluid flowing through the flow gaps and another fluid flowing within the plate pairs. This is especially the case when the flow gaps of the first and second subsets are alternatingly arranged along the stacking direction, so that each plate pair has one of the first subset of flow gaps on one side of the plate pair and one of the second subset of flow gaps on the opposing side of the plate pair. The inventors have found that, when the fluid encounters a leg of the flow baffle blocking the flow channel and is directed to flow in the transverse direction, a region of high velocity and, consequently, increased convective heat transfer occurs immediately upstream of the flow baffle in the longitudinal direction. Conversely, after the fluid passes through the gap between the terminal end of the leg and the wall of the housing and expands into the space between that flow baffle leg and the subsequent flow baffle leg in that flow channel, a region of low velocity and, consequently, decreased convective heat transfer occurs immediately downstream of the flow baffle in the longitudinal direction. In addition, the leg itself prevents the flow of fluid over that portion of the plate where it is disposed, preventing any convective heat transfer from the surface of the plate where the leg is present.

By staggering these convective heat transfer effects on any one of the plate pairs along the longitudinal direction, a more uniform rate of heat transfer along the longitudinal direction can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a plate heat exchanger in a housing, according to some embodiment of the invention.

FIG. 2 is a partially exploded perspective view of a stack of plate pairs to be used in the plate heat exchanger of FIG. 1.

FIG. 3 is a partial cut-away view of the plate heat exchanger of FIG. 1.

FIG. 4 is a perspective view of an embodiment of the plate heat exchanger of FIG. 1, with the housing and other components removed to illustrate certain details of the heat exchanger.

FIG. 5 is a section view taken along the lines V-V of FIG. 4.

FIG. 6 is the section view of FIG. 5 with certain components hidden from view for the sake of clarity.

FIGS. 7A and 7B are plan views of the embodiment of FIG. 4, showing two different flow gaps between plate pairs of the heat exchanger.

FIG. 8 is a plan view of the embodiment of FIG. 4, illustrating flow paths for a fluid through the flow gaps of FIGS. 7A and 7B.

FIG. 9 is a perspective view of another embodiment of the plate heat exchanger of FIG. 1, with the housing and other components removed to illustrate certain details of the heat exchanger.

FIGS. 10A and 10B are plan views of the embodiment of FIG. 9, showing two different flow gaps between plate pairs of the heat exchanger.

FIG. 11 is a plan view of the embodiment of FIG. 9, illustrating flow paths for a fluid through the flow gaps of FIGS. 10A and 10B.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

A heat exchanger 1 according to some embodiments of the invention is depicted in FIG. 1. The heat exchanger 1 is configured to transfer heat between a first fluid flow that enters the heat exchanger 1 through an inlet port 31 and exits the heat exchanger 1 through an outlet port 34, and a second fluid flow that enters the heat exchanger 1 through an inlet port 32 and exits the heat exchanger 1 through an exit port 33.

The heat exchanger 1 can be particularly useful in exchanging heat between two liquid flows. By way of example, the first fluid flow can be a flow of coolant such as water, ethylene glycol, propylene glycol, or a glycol-water mixture. Also by way of example, the second fluid flow can be a flow of lubricating oil, or hydraulic oil, or a combustible fuel such as LNG or LPG. In some applications the heat exchanger 1 can be used to cool the second fluid by transferring heat from the second fluid to the first fluid as they pass through the heat exchanger 1. In other applications the heat exchanger 1 can be used to heat the second fluid by transferring heat from the first fluid to the second fluid as they pass through the heat exchanger.

In some particular embodiments, the heat exchanger 1 is used as a vaporizer for LNG or LPG. The LNG or LPG enters the heat exchanger 1 through the inlet port 32 in a liquid or a two-phase liquid-vapor state, and flows through flow structures of the heat exchanger 1 while simultaneously a flow of liquid coolant enters the heat exchanger 1 and flows through other flow structures of the heat exchanger 1. As the two fluid flow through the heat exchanger, heat is convectively transferred from the higher temperature coolant to the lower temperature LNG or LPG. The transfer of heat into the LPG or LNG vaporizes the liquid fraction of the LPG or LNG, so that it exits the heat exchanger 1 through the outlet port 33 as a fully vapor state flow. The coolant exits the heat exchanger 1 at a reduced temperature though the outlet port 34.

As shown in FIG. 1 and FIG. 3, the heat exchanger 1 includes an outer housing 2 to contain the flow structures for the fluids. In the exemplary embodiment, the housing 2 is constructed of several walls, particularly walls 7-13, which are joined together to define a fluid volume 4 for the first fluid to pass through. The housing 2 can be constructed of a metal such as aluminum or steel. It should be understood, however, that the housing 2 need not be constructed of metal, and can in some instances be constructed, at least in part, of other materials such as, for example, plastic. In at least some embodiments, the housing can be provided as a part of another component. For example, the housing 2 can be provided as a cavity or sump within an engine block.

The ports 32 and 33 extend though apertures in a top wall 10 of the housing 2, thereby allowing for the connection of fluid lines to transport the second fluid into and out of the heat exchanger 1. It should be understood, however, that one or both of the ports for that fluid can alternatively be arranged on other walls of the housing 2. The port 31 extends through the wall 12 of the housing 2 and the port 34 extends through the wall 13 of the housing 2, but again it should be understood that one or both of these ports can alternatively be arranged on other walls of the housing 2. The placement of the ports 31-34 as shown in the exemplary embodiment can provide increased heat exchanger effectiveness by providing for an overall counter-flow orientation between the two fluid flows. However, in some cases it may be beneficial to rearrange the ports to achieve, for example, a concurrent-flow or parallel-flow orientation.

Arranged within the housing 2 of the heat exchanger 1 is a stack 3 of plate pairs 5, shown in the partially exploded view of FIG. 2, which is housed within the internal fluid volume 4 of the housing 2, as shown in partially cut-away FIG. 3. The plate pairs 5 are stacked together in a stacking direction, indicated by the arrow 22, to form the stack 3. Such a heat exchanger construction, referred to herein as a plate heat exchanger construction, allows for the flow of the second fluid to pass through the interior of the plate pairs 5 as the flow of the first fluid passes through the fluid volume 4. That flow of the first fluid passes through flow gaps 6 that are arranged between adjacent ones of the plate pairs 5, as will be described, so that the first fluid flows over the external surfaces of the plate pairs 5 in order to exchange heat with the second fluid as that second fluid flows through the plate pairs 5.

Each of the plate pairs 5 extends in a longitudinal direction, indicated by the arrow 20. The overall flow of both the first fluid and the second fluid are preferably aligned with the longitudinal direction, and are preferably arranged to be in counter-flow orientation with one another in order to maximize the heat exchange effectiveness. To that end, the longitudinal direction 20 is preferably greater than the transverse direction of the plate pairs 5 (indicated by the arrow 21) that is perpendicular to that longitudinal direction 20.

In order to convey the second fluid into and out of the plate pairs 5, an inlet manifold 35 extends in the stacking direction 22 through the stack 3 at a first end of the stack 3 in the longitudinal direction 20, and an outlet manifold 36 similarly extends through the stack 3 at a second end of the stack 3 in the longitudinal direction. The manifolds 35 and 36 can be at least partially defined by, for example, flanged apertures that are formed into the plates of the plate pairs 5. Annularly shaped spacer rings 37 can be arranged at in the flow gaps 6 between adjacent plate pairs 5 At the manifold locations in order to further define the manifolds. The inlet fitting 32 is aligned with the inlet manifold 35 to deliver the flow of second fluid into the manifold 35 in order to distribute that flow among the various plate pairs 5 of the stack 3, and the outlet fitting is aligned with the outlet manifold 36 in order to remove the flow from the manifold 36 after it has discharged into that manifold 36 form the various plate pairs 5.

Multiple baffles 7, shown generally in FIG. 3, are assembled to the stack 3 in order to route the first fluid through the flow gaps 6 so that the rate of heat transfer between the fluids can be increased. The baffles 7 each include legs 17 (best seen in FIG. 6), each of which extends into one of the flow gaps 6 between the plates that bound that flow gap 6, in order to block the direct passage of the first fluid at that location along the longitudinal direction 20.

The baffles 7 are comb-like baffles, with a spine 39 from which the legs 17 extend. The spine 39 extends in the stacking direction 22 of the stack 3 alongside one of the longitudinal edges of the plate pairs 5, and is preferably disposed against the adjacent wall of the housing 2 in order to block any of the fluid from bypassing the baffle 7 between the stack 3 and the housing 2. In order to enable improved bypass flow blocking in the case where the housing walls are not uniform, the spines 39 can be provided with sealing lips that conform to the housing walls.

The legs 17 extend into the flow gaps 6 in the transverse direction 21 from one of the longitudinal edges of the plate pairs 5. Preferably, the legs 17 extend for a distance that is more than half of the overall dimension of the plate pairs 5 in the transverse direction, but less than the full extent of that overall dimension. A terminal end 18 of each leg 17 is thereby spaced away from the longitudinal edge of the plate pair opposite the longitudinal edge from which the leg extends. For instance, the terminal ends 18 of those legs 17 that extend from a first longitudinal edge 15 of the plate pairs (e.g. the legs of the baffles 7 a and 7 d as shown in FIGS. 7A and 7B) are spaced away from a second longitudinal edge 16, and the terminal ends 18 of those legs 17 that extend from the second longitudinal edge 16 of the plate pairs (e.g. the legs of the baffles 7 b and 7 c as shown in FIGS. 7A and 7B) are spaced away from the first longitudinal edge 15. As a result of those spacings, the fluid is able to flow between those terminal ends 18 and a corresponding wall 8 or 9 of the housing 2, so that the first fluid can continue to flow in the longitudinal direction 20.

As can be seen in FIGS. 5 and 6, any one of the baffles 7 has legs 17 that extend into some, but not all, of the flow gaps 6. The flow gaps 6 are separated into a first subset 6 a of the flow gaps, and a second subset 6 b of the flow gaps. Preferably, the flow gaps of the first subset 6 a and the flow gaps of the second subset 6 b are alternatingly ordered along the stacking direction 22, as shown in FIG. 5. Each of the baffles 7 has legs 17 that extend into one subset of the flow gaps but not into the other one of the subsets. For example, with specific reference to FIGS. 7A and 7B, the legs of the flow baffles 7 a and 7 c extend into the flow gaps of the first subset 6 a, but not into the flow gaps of the second subset 6 b, and the legs of the flow baffles 7 b and 7 d extend into the flow gaps of the second subset 6 b, but not into the flow gaps of the first subset 6 a. Each of the flow baffles can be provided with notches 38 that allow the edges of the plate pairs to be received into the baffle 7 for proper assembly of the flow baffles 7.

In addition to having legs 17 that extend into the flow gaps 6 between adjacent plate pairs 5, the baffles 7 are also provided with an additional leg 17 that is arranged in a similar flow gap between a terminal one of the plate pairs 5 and an adjacent wall of the housing 2. The flow baffles 7 a and 7 c have such an additional leg 17 that extends into a flow gap between the terminal plate pair 5 at a first end 23 of the stack and an adjacent wall 10 of the housing 2, while the flow baffles 7 b and 7 d have such an additional leg 17 that extends into a flow gap between the terminal plate pair 5 at a second end 24 of the stack and an adjacent wall 11 of the housing 2.

The flow baffles can be arranged in a pattern along the longitudinal direction 20 so that a sinusoidal flow pattern of the first fluid through the flow gaps is developed. The sinusoidal pattern that is developed in the first subset of flow gaps can be independent of the sinusoidal pattern that is developed in the second subset. FIG. 8 represents the path of fluid through the flow gaps of the first subset 6 a with the meandering solid arrow 29, and the path of fluid through the flow gaps of the second subset 6 b with the meandering dashed arrow 30.

The sinusoidal flow path 29 results from a repeating pattern by which the baffles 7 a and 7 c are arranged along the longitudinal direction 20. As shown in FIG. 7A, the flow baffles 7 a and 7 c (i.e. the flow baffles 7 with legs that extend into the first subset of flow paths 6 a) are alternatingly arranged at a regular interval along the longitudinal direction 20. A flow baffle 7 a is followed by a flow baffle 7 c that is spaced some further distance along the longitudinal direction 20, followed by another flow baffle 7 a that is again spaced some further distance along. This pattern can repeat itself additional times along the length of the plate pairs in the longitudinal direction 20, but (as is seen in the embodiment of FIG. 4) it need not repeat. The period of the sinusoidal flow pattern is determined by the distance between subsequent occurrences of the same flow baffle (e.g. the flow baffle 7 a). It should be noted that, while the exemplary embodiment of FIGS. 4-8 show a constant spacing between the flow baffles of a given subset of flow gaps, in some alternative embodiments a non-constant spacing can be used, in which case the sinusoidal flow path will have a non-constant period.

In a similar fashion, as shown in FIG. 7B, the flow baffles 7 b and 7 d (i.e. the flow baffles 7 with legs that extend into the second subset of flow paths 6 b) are alternatingly arranged at a regular interval along the longitudinal direction 20 in order to create the sinusoidal flow path 30 within those flow gaps. In the exemplary embodiment of FIGS. 4-8, the baffles 7 b are aligned, along the longitudinal direction 20, with the baffles 7 a, and the baffles 7 d are similarly aligned with the baffles 7 c. As a result, the sinusoidal flow paths 29 and 30 both have the same period, and are phase-shifted from one another by approximately 180°.

FIG. 9 depicts an alternative embodiment of a plate stack 3′ that can be used within the heat exchanger 1. The plate stack is constructed using the same plate pairs 5 as the stack 3, but has a different arrangement of comb-like baffles 7. As shown in FIGS. 10A and 10B, the stack 3′ also has flow baffles 7 a and 7 c that have legs extending into the flow gaps of a first subset 6 a′, and flow baffles 7 b and 7 d that have legs extending into the flow gaps of a second subset 6 b′. The baffles 7 a and 7 c again are alternatingly arranged along the longitudinal direction with a constant spacing, and extend into the flow gaps from opposing longitudinal edges 15 and 16, respectively. Likewise, the baffles 7 b and 7 d again are alternatingly arranged along the longitudinal direction with a constant spacing, and extend into the flow gaps from opposing longitudinal edges 16 and 15, respectively. Accordingly, as depicted in FIG. 11, sinusoidal flow patterns 29′ and 30′ are produced within the subsets 6 a′ and 6 b′, respectively.

In contrast with the embodiment of FIG. 4, however, the flow baffles with legs extending into the second subset 6 b′ are staggered, in the longitudinal direction, from the flow baffles with legs extending into the first subset 6 a′, resulting in a phase-shift between the flow patterns 29′ and 30′ that is less than 180°.

In the embodiment of FIG. 9, the flow baffles 7 are arranged in a fully staggered, repeating pattern whereby, along the longitudinal direction, a first flow baffle 7 a is followed by a second flow baffle 7 b followed by a third flow baffle 7 c followed by a fourth flow baffle 7 d, followed again by another instance of that pattern. It can further be seen, in FIGS. 10A and 10B, that the spacing in the longitudinal direction between a baffle 7 a and the subsequent baffle 7 b is greater than the spacing between that baffle 7 b and the subsequent baffle 7 c. Furthermore, the spacing between a baffle 7 c and the subsequent baffle 7 d is the same as the spacing between a baffle 7 a and the subsequent baffle 7 b, and the spacing between a baffle 7 d and the subsequent baffle 7 a is the same as the spacing between a baffle 7 b and the subsequent baffle 7 c. This spacing pattern has the result that the phase shift between the flow patterns 29′ and 30′ is less than 90°. In the case where all the spacings are equal, the phase shift would be equal to 90°.

The flow gaps 6 between adjacent ones of the plate pairs 5 can be created through a pattern of outwardly directed dimples 14 that are formed into the plates. These dimples 14 are arranged in a regularly repeating array, and are further arranged so that the locations of the dimples on adjacent plate pairs 5 coincide with one another, so that the plate pairs 5 can be joined together (for example, by brazing) to form the completed stack 3 or 3′ with the requisite flow gaps 6. The legs 17 of the comb-like flow baffles 7 can be sized to have a height that is generally equal to twice the height of the dimples 14 (with some allowance for manufacturing tolerances) so that the legs 17 can fill the gap between the plate pairs 5 in order to block the flow of the first fluid.

The pattern of the dimples 14 is such that the dimples 14 are arranged in rows that extend in the transverse direction 21, with the rows spaced apart, in the longitudinal direction 20, to provide spaces for the legs 17 of the flow baffles 7. The spacing between flow baffles 7 can, then, be expressed as an integer multiple of the spacing between transverse rows of the dimples 14. In the exemplary embodiment of FIG. 9, as can be seen from FIGS. 10A and 10B, the period of the sinusoidal flow path 29′ (equal to the spacing between successive ones of the first flow baffles 7 a) and the period of the sinusoidal flow path 30 (equal to the spacing between successive ones of the second flow baffles 7 b) are both equal to six dimple row spacings. Each dimple row spacing is, therefore, equal to a 60° portion of the sinusoidal path.

If those flow baffles 7 whose legs extend from the same longitudinal edge of the plate pairs 5 (e.g. the flow baffles 7 b and 7 c) were to be aligned in pairs along the longitudinal direction, then the phase shift between the sinusoidal flow patterns would be zero. Consequently, the phase shift can be calculated by the offset between the baffle 7 b and the baffle 7 c of an instance of the repeating pattern, or by the offset between the baffle 7 d of one instance and the baffle 7 a of the subsequent instance. In the exemplary embodiment of FIG. 9, that offset is equal to a single dimple row spacing, which is equivalent to a phase shift of 60°.

By causing the first fluid to flow in a sinusoidal pattern through the flow gaps 6, the heat transfer performance of the heat exchanger 1 is improved. This is at least in part due to higher Reynolds numbers in the fluid flow immediately upstream of each baffle 7, where the flow of fluid is directed from the longitudinal direction 20 to the transverse direction 21. The inventors have found that, once the fluid flows through the gap between the end 18 of the flow baffle legs and the opposing wall of the housing 2 to continue on in the longitudinal direction 20, a “dead zone” of low Reynolds number flow is formed immediately downstream of the baffle. The rate of convective heat transfer is thus reduced in this region immediately downstream. While such an undesirable decrease in local heat transfer performance can be partially remedied by increasing the number of flow baffles, and decreasing the spacing therebetween, such a modification would increase the pressure drop through the heat exchanger, which is often undesirable.

By offsetting the baffles on adjacent ones of the flow gaps 6, the zones of low convective heat transfer on one outwardly facing surface of each plate pair 5 can be aligned with the zones of high convective heat transfer on the other outwardly facing surface of the pair. This allows for a more uniform rate of heat transfer that is higher than would be achieved without flow baffles.

In some applications, the increased rate of heat transfer resulting from the described baffle arrangements might only be necessary over a portion of each plate pair. For instance, it may be desirable to provide the increased rate of heat transfer only at an end of the stack 3 in the longitudinal direction 20 (i.e. near the inlet port 31 or the outlet port 32) in order to provide enhanced heat transfer in a region of the heat exchanger 1 that otherwise would have limited heat transfer effectiveness due to a reduced approach temperature difference between the two fluids in that region.

The heat exchanger 1 can find particular utility as a vaporizer for LNG or LPG. In such an application, the LNG or LPG would be the fluid that is directed to flow through the plate pairs 5, while liquid coolant flows through the flow gaps 6 in order to transfer heat to the LNG or LPG, thereby vaporizing the fluid. The LNG or LPG enters the heat exchanger 1 at a very low temperature, which can create a risk of freezing the liquid coolant near the inlet port 32 of the LNG or LPG. By providing the baffles as described, particularly in that region, the risk of freezing can be reduced.

While the legs 17 as depicted in the exemplary embodiments extend perpendicularly to the longitudinally extending edges 15 and 16 of the plate pairs 5, the legs 17 can alternatively extend in the transverse direction 21 in a non-perpendicular fashion. For example, it can be observed that the dimples 14, in addition to being arranged in rows that run in the transverse direction 21, are also arranged in rows that run at an approximately 45° angle to both the transverse direction 21 and the longitudinal direction 20. In some applications it may be desirable for the legs 17 of the baffles 7 to extend into the flow gaps along such an angle. In such an embodiment, the legs 17 would still extend into the flow gaps 6 to create a sinusoidal flow pattern, as they would still be extending in the transverse direction from one of the edges 15, 16. Furthermore, the dimple pattern can be adjusted to provide dimple rows at angles other than 45°.

Various alternatives to the certain features and elements of the present invention are described with reference to specific embodiments of the present invention. With the exception of features, elements, and manners of operation that are mutually exclusive of or are inconsistent with each embodiment described above, it should be noted that the alternative features, elements, and manners of operation described with reference to one particular embodiment are applicable to the other embodiments.

The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention. 

What is claimed is:
 1. A plate heat exchanger comprising: a housing defining a volume for a fluid to flow through; a stack of plate pairs arranged within the housing, each plate pair having a longitudinal direction and a transverse direction, the dimension of the plate pairs in the longitudinal direction being greater than the dimension of the plate pairs in the transverse direction; a plurality of flow gaps arranged between adjacent ones of the plate pairs in a stacking direction of the stack and between outermost ones of the plate pairs and walls of the housing, the plurality of flow gaps consisting of a first subset of the plurality of flow gaps and a second subset of the plurality of flow gaps, the flow gaps of the first subset and the flow gaps of the second subset being alternately ordered in the stacking direction; and a plurality of comb-like baffles extending into the plurality of flow gaps in order to define a sinusoidal flow path for the fluid extending in the longitudinal direction within each one of the flow gaps, wherein the sinusoidal flow paths in the flow gaps of the second subset are phase-shifted from the sinusoidal flow paths in the flow gaps of the first subset.
 2. The plate heat exchanger of claim 1, wherein the sinusoidal flow paths in flow gaps of the second subset are phase-shifted from the sinusoidal flow paths in the flow gaps of the first subset by no more than 90°.
 3. The plate heat exchanger of claim 1, wherein the sinusoidal flow paths in flow gaps of the second subset are phase-shifted from the sinusoidal flow paths in the flow gaps of the first subset by 60°.
 4. The plate heat exchanger of claim 1, wherein the plate pairs are provided with an array of outwardly directed dimples, adjacent ones of the plate pairs being joined together through the dimples, the dimples being arranged in rows that extend in the transverse direction, and wherein the comb-like baffles are arranged between the rows of dimples.
 5. The plate heat exchanger of claim 1, wherein the plurality of comb-like baffles are arranged in a repeating pattern along the longitudinal direction.
 6. The plate heat exchanger of claim 5, wherein an instance of the repeating pattern consists of four of the comb-like baffles.
 7. The plate heat exchanger of claim 5, wherein the repeating pattern includes a first comb-like baffle extending from a first longitudinal edge of each plate pair, followed by a second comb-like baffle extending from a second longitudinal edge of each plate pair, followed by a third comb-like baffle extending from the second longitudinal edge of each plate pair, followed by a fourth comb-like baffle extending from the first longitudinal edge of each plate pair.
 8. The plate heat exchanger of claim 7, wherein a spacing in the longitudinal direction between said first comb-like baffle and said second comb-like baffle is greater than a spacing in the longitudinal direction between said second comb-like baffle and said third comb-like baffle.
 9. A plate heat exchanger comprising: a housing defining a volume for a fluid to flow through; a stack of plate pairs arranged within the housing, each plate pair having a longitudinal direction and a transverse direction, the dimension of the plate pairs in the longitudinal direction being greater than the dimension of the plate pairs in the transverse direction, adjacent ones of the plate pairs being spaced apart to define a plurality of flow gaps between the plate pairs for the fluid to pass through, each one of the plate pairs having a first edge and a second edge both extending in the longitudinal direction; one or more first flow baffles arranged within the housing, each of the one or more first flow baffles having a plurality of legs extending in the transverse direction from the first edges of the plate pairs into a first subset of the plurality of flow gaps but not into a second subset of the plurality of flow gaps, said plurality of legs extending more than half of the dimension of the plate pairs in the transverse direction, terminal ends of said plurality of legs being spaced away from the second edges of the plate pairs to allow the fluid to flow between said terminal ends and a wall of the housing adjacent to the second edges; one or more second flow baffles arranged within the housing, each of the one or more second flow baffles having a plurality of legs extending in the transverse direction from the second edges of the plate pairs into the second subset of flow gaps but not into the first subset of flow gaps, said plurality of legs extending more than half of the dimension of the plate pairs in the transverse, terminal ends of said plurality of legs being spaced away from the first edges of the plate pairs to allow the fluid to flow between said terminal ends and a wall of the housing adjacent to the first edges; one or more third flow baffles arranged within the housing, each of the one or more third flow baffles having a plurality of legs extending in the transverse direction from the second edges of the plate pairs into the first subset of flow gaps but not into the second subset of flow gaps, said plurality of legs extending more than half of the dimension of the plate pairs in the transverse direction, terminal ends of said plurality of legs being spaced away from the first edges of the plate pairs to allow the fluid to flow between said terminal ends and a wall of the housing adjacent to the first edges; and one or more fourth flow baffles arranged within the housing, each of the one or more fourth flow baffles having a plurality of legs extending in the transverse direction from the first edges of the plate pairs into the second subset of flow gaps but not into the first subset of flow gaps, said plurality of legs extending more than half of the dimension of the plate pairs in the transverse, terminal ends of said plurality of legs being spaced away from the second edges of the plate pairs to allow the fluid to flow between said terminal ends and a wall of the housing adjacent to the second edges.
 10. The plate heat exchanger of claim 6, wherein the flow gaps of the first subset and the flow gaps of the second subset are alternatingly arranged in a stacking direction of the stack.
 11. The plate heat exchanger of claim 7, wherein the housing includes a wall that is spaced apart from a terminal one of the plate pairs at a first end of the stack in the stacking direction to define a flow gap for the fluid to pass through, and wherein each of the one or more first flow baffles and each of the one or more third flow baffles have an additional long leg that extends in the transverse direction into that flow gap.
 12. The plate heat exchanger of claim 8, wherein the housing includes a wall that is spaced apart from a terminal one of the plate pairs at a second end of the stack in the stacking direction opposite the first end to define a flow gap for the fluid to pass through, and wherein each of the one or more second flow baffles and each of the one or more fourth flow baffles have an additional long leg that extends in the transverse direction into that flow gap.
 13. The plate heat exchanger of claim 6, wherein each of the one or more first flow baffles is aligned with one of the one or more second baffles in the longitudinal direction and wherein each of the one or more third flow baffles is aligned with one of the one or more fourth baffles in the longitudinal direction.
 14. The plate heat exchanger of claim 6, wherein the first, second, third, and fourth flow baffles are all staggered along the longitudinal direction.
 15. The plate heat exchanger of claim 11, wherein the first, second, third, and fourth flow baffles are arranged in a repeating pattern along the longitudinal direction
 16. The plate heat exchanger of claim 12, wherein the repeating pattern consists of one of the first flow baffles followed by one of the second flow baffles followed by one of the third flow baffles followed by one of the fourth flow baffles.
 17. The plate heat exchanger of claim 13, wherein a spacing in the longitudinal direction between the first and the second flow baffles of the repeating pattern is greater than a spacing in the longitudinal direction between the second and the third flow baffles of the repeating pattern.
 18. The plate heat exchanger of claim 14, wherein the spacing in the longitudinal direction between the first and the second flow baffles of the repeating pattern is exactly twice the spacing in the longitudinal direction between the second and the third flow baffles of the repeating pattern.
 19. The plate heat exchanger of claim 14, wherein a spacing in the longitudinal direction between the third and the fourth flow baffles of the repeating pattern is equal to the spacing in the longitudinal direction between the first and the second flow baffles of the repeating pattern.
 20. The plate heat exchanger of claim 14, wherein a spacing in the longitudinal direction between the fourth flow baffle of one instance of the repeating pattern and the first flow baffle of an immediately following instance of the repeating pattern is equal to the spacing in the longitudinal direction between the second and the third flow baffles of the repeating pattern. 